The disclosure concerns a printing system. In particular, the disclosure concerns a printing system that has at least two printing units to apply printing ink onto a recording material, wherein each printing unit has multiple apparatuses with a respective microprocessor controller, wherein the microprocessor controllers of one printing unit are connected with one another with a respective data bus.
A typical data bus to control apparatuses is the CAN bus. The abbreviation CAN stands for Controller Area Network. Individual bus participants (which are electrical modules or structural assemblies) of an apparatus (for example a printing device) are connected with one another with the CAN bus. The CAN bus is a simpler, more cost-effective, serial data bus with which data can in fact be transferred very simply but with a relatively low transfer rate within the scope of microprocessors. According to the CAN protocol, to transmit data the data are distributed in multiple telegrams, wherein each telegram comprises a data block and an identifier.
The CAN bus or the corresponding protocol is explained in detail in “CAN—Controller Area Network, Grundlagen and Praxis”, W. Lawrenz (Ed.), 2nd edition, 1997 (ISBN 3-7785-2575-1) on Pages 86 through 95. A CAN bus is typically realized with a differential electrical two-wire conductor. A CAN data telegram can comprise a start bit; an identifier comprising 11 bits; 7 additional control bits; 0 to 8 data bytes; and additional control bits that follow the data bytes. The structure of a CAN data telegram can differ depending on the version of the CAN specification.
The arbitration is executed per bit and without control. This means that the sender (which takes precedence relative to other senders in the data bus due to its priority) does not need to resend its telegram. For arbitration, the control bits provided by the data bytes are used, wherein the arbitration essentially takes place via the bits of the identifier. From “Associate Identifier and Exchange Messages”, (ISBN 3-8259-1902-1) 1st edition, 1998, PRAXIS Profiline—Controller Area Network (CAN), Pages 40 to 43, it arises that the type of the identifier specification can be designated as a fundamental structural element of CAN-based systems since the identifier defines a CAN message, its relative priority and thus its latency time. Moreover, the scheme of the association of identifiers with CAN messages ultimately determines the communication structure of the network.
In what is known as a CANopen network, an apparatus-oriented allocation scheme for identifiers which enables a data exchange between a superordinate control apparatus (master) with up to 127 slave apparatuses is provided with what is known as a “minimal apparatus configuration”. The maximum number of participants in such a CANopen network is 128. This number of participants is limited by the 11-bit identifier.
In Zeltwanger, Holger “Everyone Can Send and All Receive: CAN Communication and Bus Arbitration”, (ISBN 3-8251-1902-1) 1st edition, 1998, Praxis Profiline—Controller Area Network (CAN), Pages 5-7, the difference between the data telegrams with standard frames that have the 11-bit identifier and with the extended frames that have the 29-bit identifier is explained in detail.
A device for a conductor termination of 2-wire conductors, in particular for a CAN bus system, arises from WO 2004/062219 A1. This device has a first and second terminating resistor between the two wires of the data line, wherein the first and second terminating resistor are connected in series. Switches that are activated by a control logic are provided between the two terminating resistors. The control logic is connected with a microcontroller so that, after receiving a corresponding signal from the microcontroller, the control logic can operate the switches arranged between the terminating resistors. The configuration of the terminating resistor can thus be changed at any time with the microcontroller. Alternatively, an adaptation of the terminating resistor in hardware is provided by means of a bridge in the cable harness plug.
A branching device for a data bus (a CAN bus, for example) arises from WO 02/056545 A2. Individual branches can be uncoupled or coupled in a star bus topology with this branching device. This is possible during the operation of the data bus. This branching device has an interface converter, a transmission and reception unit and one or more terminating resistors.
A method to connect bus participants to an existing CAN bus is known from WO 2007/122229 A2. In this method, upon connecting new bus participants preliminary participant identification numbers are determined using the serial numbers of the respective bus participant; these are used as identifiers for bus messages with which the allocation of final participant identification numbers is executed. The final participant identification numbers are shorter than the serial numbers, which is why it is possible in the ultimate operation to use bus messages with correspondingly short identifiers.
A data bus system is presently considered that is designed such that, solely via the connection of a new bus participant with a bus cable to an existing data bus, the data bus is automatically terminated with the correct characteristic impedance.
Complex apparatuses (high-capacity printers, for example) are most often modular in design. It should hereby be possible to add or remove individual modules or structural groups as simply as possible. These modules and structural groups should hereby also be coupled to or decoupled from a data bus that is possibly present.
From U.S. Pat. No. 6,865,460 B2, a “segmented” CAN bus arises in which an address is associated with each individual node so that the bus topology can automatically be detected. The nodes thus must be provided with electronic structural elements which can store the addresses and from which the addresses can be polled.
What are known as CAN repeater switching elements are distributed by the company IXXAT Inc., 120 Bedford Center Road, Bedford, N.H. 03110, USA., www.ixxat.com, for example under the commercial name “CAN-CR200 Modular ISO 11898-2 CAN Repeater”; see for example www.ixxat.com/can_cr200_en.druck, downloaded by the applicant on 19 Jan. 2011.
These are switching elements to connect CAN buses with which data can be transferred across CAN busses that are physically separate in design. These switching elements electrically decouple the individual CAN buses, wherein they logically link them with one another, however. However, what is disadvantageous with such switching elements is that they decrease the maximum data transfer rate that is possible in a CAN bus. Given applications in which a data bus should be used with the maximum possible data transfer rate, such switching elements are unsuitable. In high-capacity printing systems, due to the plurality of apparatuses to be connected high data transfer rates are necessary, such that the use of conventional switching elements often appears to be unwise.
In the related U.S. Patent Application case no. P11,0344 filed Jan. 24, 2011 and the title “Tandem Printing System and Method to Control a Tandem Printing System, and Computer System, and Computer Program Product” that was submitted by the applicant at the same time as this Application, a tandem printing system is described whose two printing apparatuses are selectively operable individually or jointly. For this, at least one of the printing apparatuses has an activation operating unit with which at least one of the printing apparatuses can be selectively activated for its individual operation or both printing apparatuses can be activated for the tandem operation.
The aforementioned disclosures or the contents of the Patent Applications are herewith incorporated by reference into the present Specification.
A printing system with a CAN bus to which multiple apparatuses can optionally be connected is known from US 2003/0131159 A1. After the connection the terminating resistor is respectively reset by means of a controller.
Multifunction printing apparatuses with a respective scan device that can be operated in a tandem mode and for this are connected with one another via an IEEE13941 network are known from US 2004/0263903 A1. If the tandem mode is selected in a control panel by a user, controllers of the respective participating apparatuses are then set accordingly.
A method to configure a CAN bus system is known from U.S. Pat. No. 5,034,878 A.
A CAN bus system that is subdivided into multiple sections is known from U.S. Pat. No. 6,151,298 A. The sections can be connected with one another via connection circuits.